In general, in gear machining by a machine tool, after machining by cutting, grinding, and the like, a pitch error, a tooth shape error, a tooth trace (a crossing line of a tooth surface and a pitch surface) error, and the like of the gear are measured by a gear measuring device, an error due to the machine tool or a tool is found by data of the measurement, and the machine tool or the tool is correctly adjusted. Usually, when a gear is molded through rolling by a round die, after trial rolling, the rolled gear is measured by a gear measuring device, the round die is redesigned and reground according to an error obtained by the measurement, and a desired tooth shape of the gear is obtained with high accuracy.
There are various profile deviations of gears. Helix deviations are specified by the Japan Industrial Standard (JIS) as well. By measuring helix deviations in the gear measuring device, for example, in the case of a spur gear, it is possible to measure an error of formation of a lead inclining with respect to a spur gear center axis by a helix, an error of tapering of the helix, and the like. With the gear measuring device, it is also possible to measure a shape of a crowning in which both ends of the spur gear are formed as slight curved surfaces to be thinned. To correct these errors and the like, clamp bolts for fixing a supporting table, a turning table, and the like, which support the round die, are loosened, an angle is adjusted by an angle adjustment screw, and turning angles and positions of the supporting table, the turning table, and the like are adjusted in order to adjust a turning angle on an inclined shaft (an A shaft) turned around a pushing-in direction (an X axis) for pushing in the round die and a turning angle on a taper shaft (a B shaft) turned around a Y axis. That is, an operator alternately repeats work for adjusting an attachment angle, a position, and the like of the round die and performing trial turning again to modify a desired helix.
When the turning angles are adjusted, since the turning angles are very small angles and the mass of the supporting table is large and a frictional force is also large, as adjustment for moving the supporting table, fine adjustment is difficult because a load of the supporting table is large and the supporting table easily bends. The adjustment needs to be performed by operating a clamp bolt, an angle adjustment screw, a position adjustment screw, and the like with a technique and a skill of a skilled person. The accurate angle adjustment and position adjustment are not easy for a non-skilled person. Conversely, it is also likely that an error is caused because the inclined shaft (the A shaft) and the taper shaft (the B shaft) can be moved and adjusted. There is a demand for development of a rolling machine that can facilitate adjustment of the inclined shaft (the A shaft) and the taper shaft (the B shaft) and can perform adjustment of a helix, a profile, and the like actively making use of an adjustment function. On the other hand, the applicant proposed a structure including four columnar guide surfaces in a guiding section (a guide section) in order to avoid, as much as possible, deformation of a machine body during rolling by a round die to which a high load is applied (see Patent Literature 1). In general, in a rolling machine by a round die, to avoid deformation of a supporting table that supports the round die, a bar material for deformation prevention called stay bolt is laid over in an upper part between left and right supporting tables.
The four guiding sections of the rolling machine or a stay bolt structure has a drawback in that a raw material, which is a workpiece to be rolled, is prevented from being carried in/out because the guiding sections or the stay bolt becomes an obstacle. However, for the rolling machine for the gear, it is undesirable to remove the guiding sections or the stay bolt to reduce the rigidity of the machine body. Further, these rolling machines are not always optimum as the rolling machine for the gear. That is, these rolling machines have an angle adjusting function in the taper shaft (the B shaft) direction important for the rolling of the gear but are manually adjusted and do not have an automatic adjustment function. In the machining of the gear by the rolling machine in the past, a tooth surface and the like of the gear to be rolled are different in a position in an axial direction. Therefore, in order to correct the difference, there has been proposed a method of adjusting a shape error of the tooth surface in the axial direction by regularly and reversely rotating the round die (see Patent Literature 2). This method has a drawback in that a machining time is long because the round die is reversely rotated. The method equalizes the shape error in the axial direction and cannot perform fine adjustment.